The role of immunologic mechanisms in the perpetuation of chronic viral hepatitis is being studied and the effects of different therapies for chronic viral hepatitis on the immune system are being evaluated. The role of interferon in the etiology and treatment of chronic viral hapatitis is also being assessed. Alpha interferon production by lymphocytes of patients with untreated chronic type B hepatitis is decreased and when such patients are treated with high doses of interferon alpha interferon production by lymphocytes is decreased further. When a subgroup of patients with chronic type B hepatitis, whose lymphocytes synthesize appreciable quantities of immunoglobulins and are particulary responsive in proliferation assays, are treated with interferon serum markers of hepatitis B viral replication disappear. Interferon therapy in responders was associated with a decrease in immunoglobulin production by lymphocytes. Receptors for interferon on peripheral blood mononuclear cells are being characterized.